The Effect of Laboratory Testing Duration on Copper Phytotoxicity in Industrially Polluted Soils

Metals phytotoxicity assessment in soils is predominantly based on laboratory testing. In this paper, we evaluated the effect of the duration of laboratory testing on copper toxicity levels, in ryegrass (Lolium perenne L.) grown in soils polluted by copper mining. Laboratory testing was carried out according to the protocols of ISO 11269-2, 2012 (for 21 days) and ISO 22 030, 2005 (for 60 days). When tested for 21 days, the soil copper content had no statistically significant effect on plant growth or on the ryegrass shoot copper content. Conversely, when tested for 60 days, plant growth was inversely proportional to the total soil copper content and to the soil exchangeable copper concentration. Therefore, short-term testing underestimated copper phytotoxicity. The results of this study demonstrate that long-term laboratory testing is required to realistically predict metal toxicity in plants grown under the real conditions of natural and agricultural ecosystems.